Schematic of the acetylation and methylation enzymes affecting transcription. Upper panel shows the active transcription state for chromatin with unmethylated CpG sites on the DNA and acetylated histone sites. Bottom panel shows the inactive transcription state for chromatin with methylated CpG sites and non-acetylated histone H3 lysine residues. HATs, histone acetyltransferase; HDACs, histone deacetylase; DNMTs, DNA (cystosine-5) methyltransferase; MBDs, methyl-CpG binding domain protein 2; H3, histone lysine residue; M, methylated CpG site.